The structures of Cun-1Au clusters are examined using the genetic algorithm, and the static polarizabilities and optical absorption spectra are investigated by first principles computations within the static and time-dependent versions of the density functional theory. The static polarizabilities decrease after being doped by one Au atom due to the strengthened screening effect of d electrons, which can also be weakened by three-dimensional structures. The optical spectra computed within the time-dependent density functional theory indicate that the screening effect also leads to the quenching of oscillator strengths. A deeper analysis of d-orbit indicates d-orbit is the main contributor in the optical excitation while its growing up is not directly influenced by the strengthened screening effect. The research on Cu6-nAun (n=0–6) clusters in a fixed size system verifies our arguments further. Our calculation results are in good agreement with the experimental data on the optical absorption spectra, which are closer to the experimental data than the earlier theoretical results.